In general, cheese making is a fermentation process, wherein a bacterial starter culture is added to milk, followed by the addition of a coagulating enzyme, such as rennin. Coagulation of the milk forms a curd which includes a substantial amount of whey which is mostly water. The wet curd is cut into cubes and free-whey, not trapped in the curd, is drained away. Fermentation of the curd is allowed to proceed until a particular acidity is reached and then the fermented curd may be salted to extract additional whey. The partially dried curd is molded into blocks and residual whey trapped in the block is removed by pressing. It is usually in the molds that the cheese is cured to produce a particular aroma, texture and flavor.
Although the above process can be accomplished in batches which produce relatively small blocks of cheese, it is more economical and thus more common to make large blocks of cheese, for example, 600 lbs. or more, and thereafter later process the large blocks into smaller units. Such large scale cheese production requires equipment capable of handling the large blocks and involves various production problems. One such problem is variation in the moisture content throughout the large blocks. Whey tends to be retained near the center of large blocks because it does not migrate quickly to the surface of the blocks where it is easily drained away. Excess moisture content influences the properties of the curd directly and can alter the fermentation and curing rates. In addition, salt migration at the center of the block may also differ from salt migration at the outside of the block. Consequently, variations in moisture content throughout a cheese block may result in unacceptable variations in cheese texture, taste and overall quality, that would make large scale cheese production impossible without proper, i.e., uniform, drainage of whey from large cheese blocks. Moreover, moisture variations make it difficult for a producer to meet standards for a cheese product, and often necessitate overcompensation of moisture content at the outside of the cheese to make up for excess moisture content near the center of the cheese block.
A common approach to dealing with moisture variation problems which occurs with large cheese blocks is insertion of a perforated, rigid structure, e.g., a blade, into the cheese curd to provide channels for drainage of whey from the central portions of the curd to its surface during pressing. For example, U.S. Pat. Nos. 3,969,952 and 4,234,615 disclose apparatus having perforated V-shaped blades that are inserted into the curd during the pressing stage to facilitate drainage of residual whey from the center portions of large blocks. The term ,drainer blade,, as used herein, refers generally to structures, such as probes, screens or the like, which are inserted into curd or cheese blocks to form channels that facilitate drainage of moisture, e.g., whey, from central portions thereof.
Other patents which describe large scale cheese production methods and equipment are U.S. Pat. Nos. 2,851,776; 2,291,064; 3,100,712; 3,133,492; 3,355,805; 3,568,316; 3,719,994 and 4,418,616.
In conventional cheese making practice, wet curd is filled into a container, usually a rectangular, plywood or cardboard, box lined with plastic sheeting having an open top and open bottom. The open bottom of the container is usually closed by a drainer pan assembly comprised of a perforated bottom drainer plate nested into a complementary shaped pan having side walls, which catches whey passing from the curd through the drainer plate. The bottom drainer plate is usually bolted to the pan, but may be attached by weldments, rivets or the like and it may further include a plurality of drainer blades which project into curd in the container. Feet projecting from the bottom of the pan are adapted to rest on a dolly for moving the container from one manufacturing station to another. After filling, the container is rolled on the dolly to a processing station where top drainer plate having a plurality of drainer blades projecting therefrom is pressed into the container through the open top to compress the curd between the top drainer plate and bottom drainer plate thus eliminating voids and forcing whey out of the curd. The pressing apparatus is preferably pivotally mounted on a frame so that the pressing apparatus itself, the container and the drainer pan assembly can be tilted onto its side, i.e., 90.degree., so that free whey pressed out of the curd is rapidly drained away.
A disadvantage of the conventional drainer pan assemblies used in large scale cheese production are the cleaning problems associated with the inaccessible crevices and spaces created by the means used to attach the bottom drainer plate to the drainer pan. As noted above, conventional designs involve a drainer pan and bottom drainer plate attachment structure that creates inaccessible spaces; that may involve threaded surfaces in contact with the curd or whey; and that make disassembly difficult. Consequently, known drainer pan assemblies are difficult to disassemble and clean. Notably, threaded surfaces present difficult cleaning problems themselves.
Since cheese is an edible product, regular cleaning is necessary to insure that the sanitary standards required by the USDA or other regulatory authorities are maintained.